Interpretive Summary: Conservation of genetic resources is often a large undertaking beyond the capabilities of any unit or system. In the broad sense, genetic resources are conserved by global cooperation and coordination. At the local level, cooperation between entities such as a NPGS unit and a botanic garden may be possible and beneficial. In the case of citrus, the main national effort in genetic conservation is at Riverside, California and involves cooperation between the USDA-ARS National Germplasm Repository for Citrus & Dates (NCGRCD) and several units within the University of California, Riverside (UCR). The main source of genetic diversity is the UCR Citrus Variety Collection (CVC), which contains approximately 900 accessions. However, this collection can not be used for distribution of vegetative material due to phytosanitary considerations. Consequently, the NCGRCD maintains a protected collection for this purpose. Another UCR program, the Citrus Clonal Protection Program (CCPP), serves as the main component for distribution of propagative materials to the industry. This complements the NCGRCD's efforts in this area for the scientific community. Both the CCPP and NCGRCD are able to introduce new accessions to the CVC in addition to their own protected collections. The UCR Citrus Breeding Program also complements these efforts by providing genetic analysis and in some cases new materials.

Technical Abstract: California maintains one of the largest and most diverse assemblages of citrus genetic resources in the world with a conservation and utilization system comprising three primary units: the Citrus Variety Collection (CVC) and the Citrus Clonal Protection Program (CCPP) at the University of California and the USDA National Clonal Germplasm Repository for Citrus and Dates (NCGRCD). The CVC is the primary citrus genetic resource in California. It is one of the most extensive collections of citrus diversity in the world, encompassing approximately 865 accessions of citrus and citrus relatives. Approximately 640 of the 865 accessions are within the sub-genus Citrus, the remaining types are included in the other 27 of the 33 related genera in the sub- family Aurantiodeae of the Rutaceae. Currently, the CVC serves as a genetic resource for 32 different research projects from scion and rootstock breeding for the improvement of commercial varieties to the study of the biological activities of citrus limonoids as anticancer agents. These projects are conducted by researchers at Riverside and other citrus-producing areas in the USA. In addition to these research projects, the NCGRCD uses the CVC as its field site to help fulfill its mission to acquire, preserve, distribute, and evaluate genetic resources. Through the distribution function of the NCGRCD, the CVC also contributes to research efforts around the world. The complementary CCPP and UCR Citrus Breeding Programs are also important components in this system.